Distillation apparatus with vacuum controlled by rate of distillate flow

ABSTRACT

DISTILLATION APPARATUS COMPRISES A VESSEL HAVING AN EVAPORATION SECTION INCLUDING A HEATING COIL FOR THE LIQUID TO BE DISTILLED; AND A CONDENSING SECTION INCLUDING A VAPOUR COOLING COIL; A HEATING MEDIUM SUPPLY TO THE HEATING COIL; A PUMP OR AIR EJECTOR FOR CREATING A VACUUM WITHIN THE VESSEL; AND A DISTILLATE OUTLET CONDUIT FROM THE CONDESNING SECTION. THERE ARE PROVIDED A SENSOR FOR SENSING THE RATE OF DISTILLATION OF LIQUID, AND A VALVE TO REGULATE THE VACCUUM WITHIN THE VESSEL, THE VALVE BEING OPERABLE BY THE SENSOR TO REGULATE SAID VACUUM IN ACCORDANCE WITH THE RATE OF DISTILLATIN WHEREBY THE RATE OF EVAPORATION AND CONSEQUENTLY DISTILLATION ARE MAINTAINED AT A DESIRED VALUE.

Maym4, 1971 F, r RANDELL 3,517,320

DISTILLATION APPARATUS WITH VACUUM coNTRoLLED BY RATE oF DISTILLATE FLowFiled NOV. 6, 1968 /l Hurm'y a United States Patent 3,577,320DISTILLATION APPARATUS WITH VACUUM CONTROLLED BY RATE F DISTILLATE FLOWForrest Thompson Randell, Glasgow, Scotland, assignor to G. & J. WeirLimited, Cathcart, Glasgow, Scotland Filed Nov. 6, 1968, Ser. No.773,885 Claims priority, application Great Britain, Nov. 24, 1967,53,475/67 Int. Cl. B01d 3/42 U.S. Cl. 202-160 4 Claims ABSTRACT OF THEDISCLOSURE Distillation apparatus comprises a vessel having anevaporation section including a heating coil for the liquid to bedistilled; and a condensing section including a vapour cooling coil; aheating medium supply to the heating coil; a pump or air ejector forcreating a vacuum Within the vessel; and a distillate outlet conduitfrom the condensing section. There are provided a sensor for sensing therate of distillation of liquid, and a valve to regulate the vacuumwithin the vessel, the valve being operable by the sensor to regulatesaid vacuum in accordance with the rate of distillation whereby the rateof evaporation and consequently distillation are maintained at a desiredvalue.

This invention relates to distillation apparatus having an evaporationsection including heating means for the liquid to be distilled, aheating medium supply to the evaporation section, a condensing sectionincluding vapour cooling means, means for creating a vacuum within thedistillation apparatus and an outlet from the condensing section fordistillate. Such distillation apparatus is referred to hereinafter asdistillation apparatus of the type aforesaid.

In distillation apparatus of the type aforesaid, it is usually arrangedthat the apparatus operates whilst a predetermined set of operatingconditions prevail within the apparatus.

These conditions may include, for example, the temperature of theheating medium, the temperature of the liquid to be distilled passing tothe evaporation section, and the pressure within the apparatus.Consequently a desired rate of evaporation can be attained andsatisfactory distillate quality can be assured. However, some of theoperation conditions may change to cause excessive evaporation -with theresult that distillate of unsatisfactory quality may be continuouslyproduced. It is an object of the present invention to obviate ormitigate this disadvantage.

According to the present invention in distillation apparatus of the typeaforesaid there are provided sensing means for sensing the rate ofevaporation of liquid, and vacuum control means actuable by said sensingmeans to regulate the vacuum within the distillation apparatus inaccordance with said rate of distillation whereby the rate ofevaporation is maintained at a desired value.

The distillation apparatus may include a distillate reservoir, an outletconduit means from the condensing section, and the sensing meansincludes means for restricting the ow of distillate from the condensingsection such that, in the event of excessive evaporation and consequentexcessive distillation, the level of distillate in the reservoir rises,the sensing means being operable by the level of distillate in saidreservoir to actuate said control means.

Preferably said air inlet is provided at the condensing section.

Preferably further, temperature sensing means are provided in theheating medium supply to the evaporation 3,577,320 Patented May 4, 1971ICC section and operatively connected to the vacuum control means,whereby the vacuum within the sections may be regulated in accordancewith the temperature of the heating medium.

An embodiment of the present invention will now be described merely byway of example with reference to the accompanying drawing which showsschematically the arrangement of a distillation plant according to thepresent invention. Referring to the drawing, distillation apparatus forproducing fresh water from salt water (brine) includes a verticallydisposed casing housing a chamber having an evaporation section 1situated at the base thereof and a condensing section 2 thereabove. Mistseparators 3 are provided at the inlet to the condensing section 2 andin the path of upowing vapour from the evaporation section 1.

A feed Water tank 4 at the base of the evaporation section 1 provides areservoir for liquid to be distilled, and a raw feed water inlet conduit5 leads into the reservoid 4. A distillate overflow conduit 6 isprovided connecting with the feed water inlet conduit 5.

A bank of vertical riser tubes 7 enclosed in an evaporation casingconnects the reservoir 4 with the vapour space 1a of the evaporationsection 1 from which excess brine can be drained through a conduit 9under the inlluence of a jet pump 10. Heating medium, which ispreferably steam or hot water, is passed into the evaporation casing 8through an inlet 11, circulates around the riser tubes 7 to causeevaporation of the brine therein and passes out again through an outlet12.

The condensing section 2 includes a reservoir 20 for vdistillate and abank of U-tubes 16 extending horizontally into the condensing section 2serving for through How of cooling water. A motor driven pump 15 isprovided to draw olf the distillate via conduits 13, 14 from thedistillate reservoir 20 and directs same to a fresh water storage tank(not shown), via conduits 28, a non-return valve 29 being in the outlet28 from the pump to prevent the sucking back of fresh water. Means forsensing the distillate quality is provided as described in theapplicants U.S. Pat. No. 3,463,706 whereby if unsatisfactory distillateis produced it is fed back to the brine reservoir.

A sub-atmospheric pressure or vacuum is maintained within the verticalchamber of the distillation apparatus by the connection of the jet pump10 additionally to the condensing section via the conduit 21 in themanner described in the applicants co-pending U.S. Ser. No. 696,579means being provided to ensure that the vacuum within the condensingsection 2 is greater than that within the evaporating section 1. Theprovision of a vacuum in the casing permits a greater rate ofevaporation for the same heat input.

To provide control of the vacuum within the vertical chamber of thedistillation apparatus an air inlet conduit 30 is provided to thecondensing section 2 and a valve 31 is included in said air inletconduit 30 to regulate the passage of air therethrough to the verticalchamber. A restrictive device 32 4with a calibrated maximum fluid flowtherethrough is intercalated in the conduit 13 and adapted such that,with excessive distillate ow in conduit 13, the level of distillate inoverflow conduit 13a will rise; the sensing means 32a will includeequipment enabling the transmission of signals to relay 33 via line 34when the level of distillate has risen appropriately in conduit 13a. Therelay 33 is operatively connected to the air valve 31 to causeappropriate movement of the valve in accordance with the distillatelevel in conduit 13a.

As an alternative to the restrictive device 32, a flowmeter may beintercalated in the conduit 13 from reservoir 20 to measure thedistillate flow. 'I'he flow-meter would contain equipment enabling thetransmission of signals to relay 33 to cause appropriate movement ofvalve 31.

Also, a temperature sensing device 35 is provided in the heating mediuminlet 11 and is connected to the relay 33 via the lines 34, 36 toadditionally regulate the air val-ve 31 by means of said relay 33 inaccordance with the heating medium temperature.

The distillation apparatus operates as follows: brine is evaporated inthe evaporation section 1 and the vapour is driven olf upwards throughthe separators 3 wherein impurities are removed; the purified vapour ispassed into the condensing section 2, and the vapour is condensed, anddistillate formed is precipitated into the distillate reservoir 20whence it is pumped to the fresh water tank. If the distillate is ofunsatisfactory quality then the procedure described in the applicantsU.S.A. Patent No. 3,463,706, is brought into operation to return theunsatisfactory distillate to the reservoir 4. Thus, the salinometer 37measures the quality o'f the distillate via distillate quality sensor 38and, if the distillate is unsatisfactory, the salinometer 37 signals theswitch 39 to stop motor 40 and the distillate returns to the reservoir 4via conduits 5, 6.

However, conditions may be prevalent within the distillation apparatus,such as for example, excessive vacuum or excessively high temperature ofthe heating medium, resulting in excessive evaporation of brine and theconsequent continuous production of distillate which will probably be ofunsatisfactory quality. The quantity of distillate condensed will ofcourse be directly proportional to the quantity of brine evaporated. Anincreased quantity of distillate will be discharged into the conduit 13;as a result the excessive quantities of distillate produced and therestrictivel device 32 will cause the liquid level in conduit 13a torise to a sufficient level to actuate the sensing means 32A;consequently, the air valve 31 will be opened appropriately by thesensing means 32A. I'f alternatively a ow-meter is used, the resultantexcessive quantities of distillate produced will cause the flow-meter tosignal the relay 33 to open air valve 31 appropriately. Air willconsequently leak into the condensing and evaporating sections 1, 2 ofthe vertical chamber, the vacuum therein will be reduced; and thethermal balance conditions within the chamber to give satisfactorydistillate Will be restored. The rate of evaporation will fall, butsatisfactory distillate will be produced.

JIn the event of the temperature of the heating medium falling, thetemperature sensing means 35 will cause actuation of the air valve 31 toreduce the vacuum within the chamber and the capacity for evaporationwill be reduced. In the case of the heating medium being the jacketcooling water of an internal combustion engine and the engine isoperating under low power conditions, then the above provisions willavoid undercooling of the jacket cooling water.

I claim:

1. Distillation apparatus comprising a casing housing Cil an evaporationsection and a condensing section including rvapor cooling means in opencommunication with the evaporation section whereby vapor flows freelyfrom the evaporation section to the condensing section; an air pump forcreating a sub-atmospheric pressure within the casing such as to permitsaid free ow of vapor between the sections; an outlet conduit from thecondensing section for outtlow of distillate; distillate ilow sensingmeans in the outlet conduit for measuring the rate of distillate outilowfrom the condensing section; an air inlet duct to the casing; and anair-bleed valve in the air inlet duct, means operatively connecting saidair-bleed valve to said distillate flow sensing means whereby theair-bleed lvalve is controlled by the distillate ow sensing means and isactuated in accordance with said rate of distillate outovv to regulatethe pressure within the casing to maintain the rate of production o'fvapor in the evaporation section at a constant value.

2. Distillation apparatus as claimed in claim 1, Wherein the distillateflow sensing means includes a distillate overow conduit in parallel andin lluid communication with said outlet conduit, a restriction in theoutlet conduit downstream of the overliow conduit whereby, in the eventof an excessive rate of flow of distillate in theoutlet conduit, thelevel of distillate in the overflow conduit rises, and an actuatorresponsive to the level of distillate in said overflow conduit tocontrol said air-bleed valve.

3. Distillation apparatus as claimed in claim 1, wherein said air inletduct is provided at the condensing section.

4. Distillation apparatus as claimed in clairn 1, wherein theevaporation section includes heating means for distilland andtemperature sensing means are provided in a heating medium supply to theheating means of the evap oration section and operatively connected tothe air-bleed valve, whereby the pressure within the casing means may beregulated in accordance with the temperature of the heating medium.

References Cited UNITED STATES PATENTS 2,079,897 5/1937 Brown 202-2032,441,361 5/ 1948 Kirgan 202-206 3,055,810 9/1962 Skow 202-206 3,177,1254/1965 Berger 203-2 3,269,919 8/1966 Baily et al. 202-206 3,311,5433/1967 Loebel 202-206 3,389,059 6/1968 Goeldner 203-1 3,428,527 2/1969Rijnsdorp et al. 202-206 3,441,483 4/1969 Hart 203-2 WILBUR L. BASCOMB,JR., Primary Examiner U.S. Cl. X.R.

